Pre-amps, power amps and amplifier choice

Analog stage, outputs and amplification

Answers on this topic

• Can DAVE drive power amplifiers directly, and is its DAC mode any different from pre-amp mode at -3 dB?
• Should I use a pre-amp (tube or solid state), or run the Chord DAC straight into a power amp?
• Should I use the RCA or XLR line outputs on TT2 or DAVE into my amplifier?
• Which output level should I feed my amp: Qutest's 1, 2 or 3 V setting, TT2's DAC mode or gain, or the volume control?

Everything he said on this topic (51)

One-line summaries in our words, oldest first. Each link opens the original.

• 2014-04-29Watts says he uses one Hugo into small active speakers and another feeding his power amp, and advises avoiding pre-amps unless analog sources are needed. Head-Fi, Apr 2014
• 2014-06-09Watts measures 2.996V RMS at 0dBFS in preset mode and 2.112V RMS at violet, and advises feeding power amps directly without a pre-amp. Head-Fi, Jun 2014
• 2014-06-21Watts says the poster's setup is no problem for Hugo and the wiring is fine, and advises against using a pre-amp. needs context Head-Fi, Jun 2014
• 2014-06-21Watts advises feeding Hugo directly to sub and power amp; active pre-amps add distortion and noise floor modulation, passive controls add wiper and dielectric absorption problems. Head-Fi, Jun 2014
• 2014-07-26Watts says Hugo outputs up to 5V RMS with a 3V preset, advises dropping the pre-amp, and describes damping-factor tests and Hugo's 0.075 ohm output impedance. Head-Fi, Jul 2014
• 2014-09-11Watts says high power-amp gain is still better than adding a pre-amp, and he runs at green to azure into amps needing 1V RMS for full power. Head-Fi, Sep 2014
• 2014-11-13Watts says his main system has Hugo driving power amps directly, since removing the pre-amp greatly boosts transparency, though he must get up to change volume. Head-Fi, Nov 2014
• 2015-02-02Watts says Hugo TT's balanced output is for driving balanced power amps directly and declines to discuss balanced headphone drive. Head-Fi, Feb 2015
• 2015-05-18Watts says even the best pre-amp in the world would degrade transparency, so using no pre-amp is the most transparent option. Head-Fi, May 2015
• 2015-06-30Watts says Dave's wide output level and low noise make power amp gain unimportant, and Dave is single-ended because that is best for sound, though harder than differential. Head-Fi, Jun 2015
• 2016-01-24Watts compares 2 Qute and Hugo: similar on optical or coax, 2 Qute's galvanic isolation helps with a PC on USB, Hugo can feed power amps directly; output stages match. Head-Fi, Jan 2016
• 2016-03-01Watts says Dave is source-insensitive through bit-perfect data and immunity to jitter and noise, that depth needs perfect small-signal accuracy (350 dB noise shapers), so no pre-amp sounds better. Head-Fi, Mar 2016
• 2016-03-26Watts says the best pre-amp is none, and pre-amp bandwidth limiting is unnecessary with Dave because it has no significant out-of-band output. Head-Fi, Mar 2016
• 2016-05-17Watts says DAVE's DAC mode equals pre-amp mode with volume fixed at -3 dB (3 V RMS), and DAVE clips only above +4 dB, which gives 6.7 V RMS. Head-Fi, May 2016
• 2016-06-06Watts says his ADC plus DAVE at 768 kHz could beat an analog pre-amp, and describes a WTA FIR decimation filter from 104 MHz to 768 kHz for two prototypes. Head-Fi, Jun 2016
• 2017-02-05Watts says Dave driving valve power amps directly has always sounded superb and more transparent without a pre-amp, and suggests the 33 ohm balanced outputs if an amp goes unstable. Head-Fi, Feb 2017
• 2018-02-24Watts says Harrison attenuators, rated for a 600 ohm source with a 2.5k ohm load, suit 2Qute; run the longer cable to the attenuator and keep it near the amp. Head-Fi, Feb 2018
• 2018-04-02Watts says adding a pre-amp always degrades sound through capacitor softness and 2nd harmonic bloom, and Hugo 2 can drive an EAR 534 power amp perfectly. Head-Fi, Apr 2018
• 2018-04-19Watts says the best output level depends on the pre-amp's topology, as 3v may cause distortion in some; without PA20 experience, he advises trying levels by ear. Head-Fi, Apr 2018
• 2018-05-15Watts says amp mode on TT2 is for driving efficient speakers or replacing a pre-amp as a digital pre-amp, and suggests low gain mode for that. Head-Fi, May 2018
• 2018-05-18Watts says his DACs have no internal pre-amp but a single amplification stage, and removing a pre-amp always improves transparency, though pre-amps add bass softness and bloom some prefer. Head-Fi, May 2018
• 2019-01-16Asked whether TT2's RCA and XLR outputs can be used together in amp mode, for a sub and an amp, Watts says yes. Head-Fi, Jan 2019
• 2019-01-31Watts says TT2 supercaps last over 11 years, it can stay on, warm-up takes about 10 minutes, pre-amps cost transparency, and linear PSUs at best sound the same. Head-Fi, Jan 2019
• 2019-04-23Watts says TT2's low gain mode has lower residual noise, but the difference is inaudible through a power amp. Head-Fi, Apr 2019
• 2019-06-08Watts says TT2's RCA and XLR outputs can feed two systems at once, with probably negligible effect, and suggests checking by unplugging one. Head-Fi, Jun 2019
• 2020-01-06Watts says Qutest drives any amp input above 100 ohms, but an unpowered connected amp's clamp diodes may degrade linearity, so compare on, off and disconnected. Head-Fi, Jan 2020
• 2020-02-03Watts says Qutest's 2 V and 3 V settings do not differ significantly internally, so audible changes come from the pre-amp or power amp. Head-Fi, Feb 2020
• 2020-02-24Watts corrects himself: TT2's DAC mode is 2.5 V, the knee of the low-gain distortion curve, as 3 V can be too hot for many pre-amps. Head-Fi, Feb 2020
• 2020-03-09Watts says Qutest has no volume control, explains truncation, Gaussian dither and 11th-order noise shaping at 705/768 kHz, and prefers Roon volume over a pre-amp. Head-Fi, Mar 2020
• 2020-03-12Watts says Hugo 2 batteries are robust, advises using its own volume rather than a passive, and says certified USB cables suffice; heard differences are placebo or RF noise. Head-Fi, Mar 2020
• 2020-07-27Watts says TT2 can stay on 24/7, DAC mode equals low gain at -5L, and an external amp often sounds warmer from distortion and capacitor dielectric absorption. Head-Fi, Jul 2020
• 2020-08-11Watts calls amps that short inputs reckless, and says his MSI laptop beat a server, which sounded bright with false transparency from RF-induced noise floor modulation. Head-Fi, Aug 2020
• 2020-10-17Watts says yes, there is no downside to the suggestion, and though he has not heard the Ultima 5 or 6 he recommends trying them. needs context Head-Fi, Oct 2020
• 2020-12-19Watts says he worked with Zia of Tube Technology in the early 2000s, and that tubes sound good more easily but solid state can outperform them with more work. Head-Fi, Dec 2020
• 2021-01-08Watts says active ATC speakers on TT2's XLRs are fine if the input is truly balanced, as pro gear will not short balanced outputs. Head-Fi, Jan 2021
• 2021-04-18Watts describes the unit as a digital-input-only pre-amp, headphone amp or integrated amp for efficient speakers, or a DAC with fixed outputs. needs context Head-Fi, Apr 2021
• 2021-08-26Watts says TT2 in high or low gain has no significant DC output thanks to the digital DC servo, so it is safe with a DC-coupled power amp. Head-Fi, Aug 2021
• 2021-08-29Watts recommends a 768kHz ADC, plans pulse array ADC tests, favors digital volume over analog, and says grounding via Dave shorts its isolation; ground elsewhere, battery-power, or use a resistor. Head-Fi, Aug 2021
• 2022-01-31Watts says other reasons were simplifying setup alongside the new DSP and that Mojo's 3 volts is too much for many amplifiers, hence Qutest's 1, 2 and 3 volt settings. Darko.Audio 17:48
• 2022-02-22Watts says RF only degrades low-level linearity if signal-correlated, his DACs' RF output is low and uncorrelated, and analog pre-amps add coloration rather than beating Chord's volume control. Head-Fi, Feb 2022
• 2022-07-01Watts says his slide is correct: 3 V is too hot for many pre-amps or integrated amps, blue is more appropriate, and use it if it sounds smoother. Head-Fi, Jul 2022
• 2022-07-19Watts says a sub's line-level and speaker-level inputs both feed its power amp, an easy load for TT2, and guesses speaker level is best since less attenuation is the goal. Head-Fi, Jul 2022
• 2023-03-12Watts says some amps are overloaded by a 3V input, raising distortion and sounding harder without clipping, which is why Qutest has three output voltage settings. Head-Fi, Mar 2023
• 2023-08-30Watts says DAVE has RF filters on its outputs and a pre-amp adds random RF noise and noise floor modulation, so the most transparent pre-amp is none. Head-Fi, Aug 2023
• 2023-10-01Watts says with tubes you naturally get warmth. The Source AV 33:11
• 2024-02-12Watts says running TT2 into a short can damage it, as it can deliver 4A, and driving amps and subwoofers together is safe as long as TT2's output is never shorted. Head-Fi, Feb 2024
• 2024-07-12Watts says every solder joint, contact, resistor, capacitor and amplifier stage is audible, and valve gear often beats solid state because it is simpler. HIFICLUB 28:10
• 2024-09-29Watts says that with another audiophile, not using DAVE, the difference was hardly audible, and the problem turned out to be his power amp. The Source AV 15:29
• 2024-10-06Watts says the best pre-amp or power amp is none, cites TT2 sounding the same into an 8 ohm load, and says the large-power DX DAC concept is not dead. Head-Fi, Oct 2024
• 2025-01-08Watts says valve amps easily sound musical but bipolar can sound better, estimates 38 to 76 hours of Hugo M Scaler use per car battery, and says measurements ignore transients. Head-Fi, Jan 2025
• 2026-10-17Watts says Chord compared a turntable and phono stage direct to a preamp against going through Quartet and DAVE; the digital route sounded a lot better, which puzzled him. article, Oct 2026